System for the dradging of underwater sea-beds

ABSTRACT

A system for dredging underwater sea-beds includes a floating platform; a dredging tool positioned on the platform to face the water and having a system that lowers and lifts the dredging tool, further having at least three connection points associated with the platform to connect the ends of warping cables that are anchored to the shore at the opposite ends, and further having tensioning devices; a sediment collection system that collects sediment captured by the dredging tool; a system detecting the position of the platform; a system detecting the position of the dredging tool; a system detecting seabed configuration; a system detecting the quantity of sediment removed from the seabed; a remote command and control system for the system that lowers and lifts the dredging tool, a tensioning system for the warping cables; a detection system; and a system that supplies the equipment on board of the platform.

The present invention relates to the systems for the dredging, and inparticular relates to a system for the dredging of underwater sea-beds.

The water reserves in the world are often accumulated in artificialbasins.

These basins are almost entirely made up of barriers (dams) of waterwaysthat originally flowed freely in the riverbed, fed by the rainfall thataffects the catchment area.

The erosion phenomena due to the flow of water to the ground throughoutthe catchment area cause a natural flow of sediment in the waterway.Man-made barriers allow to modulate the water flow for use, but oftenconstitute a total barrier for sediment.

The sediments accumulated in the reservoirs create a series of problems:

-   -   decrease the water volume that can be modulated in the basin;    -   if near the barrier, they create hydrostatic pressures higher        than those of project;    -   if near mechanical operating devices (intake valves, gate        valves) they can compromise their perfect functioning;    -   if near the main outlets of hydroelectric plants, they can enter        and damage the wheels of the hydraulic turbines, causing serious        damage.

The sediments management therefore has a not insignificant importance inthe series of operations that affect the good management and maintenanceof a water reserve. In particular, the second and third problems concernaspects related to safety, as can be easily understood.

In the years, various techniques have been refined that solve theage-old problem of sediment management, and the techniques developed sofar can be classified as follows:

a) Sediment floating with water through the bottom discharge organs.This is feasible if the quantity of sediments is known and there is norisk of a “vortex that obstructs” the intake, a catastrophic event. Sothe probability of the event must be very low (−106). Such maneuver isfeasible only if there are no limits to the protection of the fish faunapresent downstream of the barrier. Such maneuver is not controllable, itis not possible to manage the dosage of sediments during floating.

b) Floating downstream of the barrier through a tube which sucks thesediment on the seabed and discharges it by gravity downstream. This isfeasible only if there are no limits to the protection of the fish faunapresent downstream of the barrier. Such maneuver is similar to dredging,operated with mechanical means similar to dredgers.

c) Removal of sediments with mechanical means with an empty basin. Veryexpensive operation because it interrupts the service of the basin andimpacts with the problem of “where to place thousands of cubic meters ofvery wet material”.

d) Removal of sediments with dredge. Normally quite expensive operationthat often requires special means, small dredgers that require trainedcompanies, floating pipes, mobile selection plants that operatecampaigns that are often do not solve the problem, but only operate inemergency situations.

On the sideline, engineering solutions can also be mentioned, that canbe defined as preventive and very expensive, sometimes introduced yearsafter the construction of the basin, such as the construction of tunnelsthat intercept the sediments upstream of the basin and convey themdownstream, and the sanding canals construction upstream of the basin.

Purpose of the present invention is therefore a dredging system which iscapable of operating in situations where the dimensions or drafts do notallow the use of known dredging devices, and which can operate with anextremely reduced use of personnel, offering against a high actionefficacy, both with large sediments and with substantially sandysediments.

Object of the present invention is therefore a system for dredgingunderwater sea-beds comprising:

-   -   a platform provided with flotation means, a dredging tool being        provided on the portion of said platform facing the surface of        the water, provided with means suitable for lowering and lifting        it, and being provided with at least three connection points        associated with said platform, with the ends of respective        warping cables, suitably anchored to the shore at the opposite        ends, and provided with suitable tensioning means;    -   sediment collection means collected by the dredging tool,    -   means for detecting the absolute position of said platform;    -   means for detecting the position of said dredging tool;    -   means for detecting the seabed configuration;    -   means for detecting the quantity of sediment removed from the        seabed;    -   remote command and control means of said means suitable for        lowering and lifting said dredging tool, tensioning means of the        warping cables, and detection means;    -   means for supplying the equipment on board the platform.

In one embodiment, the dredging tool is a bucket; this tool is used whenthe sediment has heterogeneous and in any case unpredictable dimensions;in this case the collection means comprise an underwater hopper whichdischarges the sediment to the ground, and the platform is moved fromthe sediment collection point to the unloading area where said hopper islocated. The platform, in its portion facing the surface of the water,will be equipped with a screen wall that surrounds the clamshell; themeans for detecting the amount of sediment removed in this case comprisea load cell coupled to the bucket lifting means, which comprise a winchmounted on the upper portion of the platform.

In an executive variant, the dredging tool is a dredging pump, and isused when the sediment is smaller than 40 mm in average diameter; thesediment collection means comprise a floating duct. In this case, theplatform only moves in the sediment collection area. The pump ispreferably an electric pump, powered by the supply means connected tothe platform. Means for detecting the mass flow rate of the dredgingpump are provided.

Means for tensioning the warping cables can be provided on board theplatform, just as they can be positioned on the ground. These tensioningmeans comprise winches, which provide means for detecting the tension ofthe warping cables, typically of the load cells.

Advantageously, said winches are made with a pulling part, comprisingtwo drums that wind the cable for a few turns and on a single layer, andan accumulating part, comprising a drum with a larger diameter than thefirst two, which wraps the cable at very low tension, a motorized pulleybeing provided upstream of the two traction drums which keeps the cableunder constant tension. On each operating winch of the warping cables,means for detecting the cable tension are provided, in the form ofsuitably positioned load cells.

Command and control means comprise a suitable software loaded on acomputer, which is interfaced with the tensioning means of the warpingcables, with the means for detecting the load of sediments removed bythe dredging tool, with the detection means the position of the dredgingtool, with the means for detecting the position of the platform, whichtypically will include a GPS device. Optical detection means will alsobe provided, such as video cameras, both surface and submerged, and winddetection means, such as anemometers, and detection of the wave state ofthe water surface, such as accelerometers.

In particular, both the warping cables and the lifting and loweringwinch of the dredging tool are numerical control machines.

Further advantages and characteristics of the system according to thepresent invention will become clear from the following description ofsome embodiments of the same yield, by way of non-limiting example, withreference to the attached drawings, in which:

FIG. 1 is a top plan view of a first embodiment of the platform systemaccording to the present invention:

FIG. 2 is a side elevation view of the platform of FIG. 1;

FIG. 3 is a top plan view of a second embodiment of the platform systemaccording to the present invention;

FIG. 4 is a side elevation view of the platform of FIG. 3;

FIG. 5 is a schematic diagram of a first embodiment of the systemaccording to the present invention; and

FIG. 6 is a schematic diagram of a second embodiment of the systemaccording to the present invention.

FIG. 1 shows a first embodiment of the platform system according to thepresent invention; 1 indicates the platform, with a triangular shape,which is connected to each of the corners to a float 201, while in thecenter there is the carter 101 which houses the lifting and loweringmeans of the dredging tool, not visible in the figure.

FIG. 2 is a side elevation view of the platform of FIG. 1; to the equalparts correspond to the same numbers. The figure shows the bucket 2,surrounded by the screen 301 which is connected to the platform 1; theflaps 211 protruding from the floats 201 which allow their connection tothe platform 1 are also visible, in addition to the flaps 221 whichinstead allow the connection of the platform 1 to the warping cables,not shown in the figure. 20 indicates the surface of the water.

FIG. 3 shows a second embodiment of the platform system according to thepresent invention; the same parts correspond to the same numbers: in thefigure, the platform 1 has winches 3 mounted at each of the corners fortensioning the warping cables, not shown in the figure. Said winches 3comprise a tensioning pulley 103, two cable pulling drums 203 and acable storage drum 303.

FIG. 4 shows the platform of FIG. 3 in side elevation; to equal partscorrespond to the same numbers. The figure shows that in this case thedredging tool is the dredging pump 4, which is lowered to the bottom bymeans of a winch, not visible in the figure, housed in the carter 101.The floats 201 are coupled together by means of the crossbar 231.

FIG. 5 shows a first embodiment of the system according to the presentinvention. Platform 1 is positioned on the body of water 20 enclosed inthe portion of shore 21, in correspondence with the sedimentaccumulation zone 22. The warping cables 406 are connected to the threeplatform corners, in correspondence with the three floats, which at theopposite end are coupled to a respective winch 6, of the type describedwith reference to FIG. 3. Platform 1, which uses as a dredging tool thebucket 2, is connected through the umbilical cable 81 to the generator8. On the platform there are also all the sensors necessary to controlthe system, namely the sensors for detecting the position of theplatform, the sensors for detecting the load of the bucket, the sensorsfor detecting the wave motion of the body of water, the sensors fordetecting the wind, the means of displaying the seabed. Instead, thecable tension sensors 406 are mounted on the winches. As shown infigure, the remote command and control unit 30 is connected to all theactive elements of the system. Near the shore there is the hopper 7 forunloading the sediment collected from the clamshell.

FIG. 6 shows a second embodiment of the system according to theinvention; to equal parts correspond to the same numbers. In the figureit can be seen that in this case the warping cables 403 are equippedwith fixed anchors 10 on the bank 21, while the end connected to theplatform 1 cooperates with the winches 3 of the type described in FIG.3. In this embodiment the dredging tool is the dredging pump 4, which isequipped with the discharge conduit 91 which pours the sediment into thecontainer 9. In this case most of the active components of the system,as listed in the previously described embodiment, are placed on theplatform, and are, in the same way as previously described, interfacedwith the command and remote control unit 30.

The functioning of dredging system according to the present inventionwill be evident from the following. Once the anchoring has beenoperated, whether by winches 6 of FIG. 5 or by the static anchors 10 ofFIG. 6, the platform is positioned on the body of water, and theposition of the sediment 22 is detected by means of suitable displayingmeans. At this point, in both cases, the dredging tool is lowered, whichtakes the sediment. In the case of bucket 2, the load cell placed on thelifting winch indicates the quantity of material removed from thebottom, and consequently the command can be given which allows thetransfer of the platform from the pick-up station to the sedimentcollection hopper 7. Once the unloading is complete, the platform willposition itself in the most suitable position to carry out thesubsequent removal of material, and so on until all the sediment presenton the bottom is removed.

Instead, in the case illustrated in FIG. 6, the dredging pump, oncelowered, sends the sediment, which in this case is of a finer nature andin any case less than 40 mm in diameter, to the floating discharge duct,which pours it into the container collection. The platform willgradually be moved to the area where sediment 22 is present until itscomplete removal, without needing to be brought ashore duringoperations.

Advantageously, the winches used on the ground or on the platform aremanufactured with a pulling part and an accumulation part of the cable.This design strategy satisfies the need not to have cables pressed fromthe upper layers, ensuring a good durability of the same, avoidingdangerous tangles of the cables on the drum, lethal in the case of anunattended system like this. The pulling part consists of two drums thatwrap the cable in well-sized grooves, for a few turns and only with alayer of cables. The cable that leaves the pulling part is accompanied,now with very low tension and under control, to the accumulating drum.The latter, with a larger diameter, wraps the cable at very low tension,avoiding crushing and therefore also tangling. Upstream of the pair oftraction drums there is a motorized pulley which tensions the cableconstantly, so that in case of abandonment of the load, no accidentaloverlaps of the same are created.

The dredging cycle, in both cases, can be programmed taking intoaccount: the configuration with geodetic references of the basin and thesediments deposited; of the mechanical characteristics of the sedimentsuch as to be able to choose the best dredging tool suitable for thispurpose; operating characteristics of the dredging system, such as thetranslation speed, the flow rate of the dredging pump, the volume of thebucket. It will also be possible to program operating cycles such as toallow the automatic removal of the sediment by optimizing the paths andremoval according to criteria of good practice.

The command and control unit, connected remotely, for example via radio,wifi, or similar systems, with the float and with any winches on theground allows the system to operate. Positions, speeds and accelerationsof the maneuvering and lifting winches can be controlled manually,semiautomatically, automatically, in a manner very similar to how thetools of machines commonly called numerical control are controlled.

The invention claimed is:
 1. A system for dredging an underwater seabed,comprising: a platform provided with flotation means; a dredging toolprovided on a portion of said platform facing water surface, thedredging tool having means for lowering and lifting the dredging tool,and at least three connection points associated with said platform, theat least three connection points connecting ends of respective warpingcables, which are anchored to a shore at opposite ends, the dredgingtool further having tensioning means for the warping cables; sedimentcollection means for sediment collected by the dredging tool; means fordetecting a position of said platform; means for detecting a position ofsaid dredging tool; means for detecting seabed configuration; means fordetecting a quantity of the sediment removed from the seabed; remotecommand and control means of said means for lowering and lifting saiddredging tool, the tensioning means for the warping cables, and themeans for detecting the absolute position of the platform, the positionof the dredging tool, the seabed configuration, and the quantity of thesediment removed from the seabed; and means for supplying equipment onboard the platform.
 2. The system according to claim 1, wherein thedredging tool is a bucket, the sediment collection means comprising anunderwater hopper which discharges the sediment to the ground, theplatform being moved the sediment collection point to a discharge areawhere said underwater hopper is located.
 3. The system according toclaim 2, wherein the platform, in the portion facing the water surface,is provided with a screen wall that surrounds the bucket.
 4. The systemaccording to claim 2, wherein the means for detecting the quantity ofthe sediment removed from the seabed comprise a load cell coupled to themeans for lowering and lifting the dredging tool.
 5. The systemaccording to claim 2, wherein said means for lowering and lifting thedredging tool comprise a winch mounted on an upper portion of theplatform.
 6. The system according to claim 1, wherein the dredging toolis a dredging pump, and the sediment collection means comprise afloating duct.
 7. The system according to claim 6, wherein the dredgingpump is an electric pump, powered by feeding means connected to theplatform.
 8. The system according to claim 6, further comprising meansfor detecting a mass flow rate of the dredging pump, which are arrangedalong said floating duct.
 9. The system according to claim 1, whereinsaid tensioning means for the warping cables are provided on theplatform.
 10. The system according to claim 1, wherein said tensioningmeans for the warping cables are positioned on the shore.
 11. The systemaccording to claim 9, wherein said tensioning means comprise winches.12. The system according to claim 11, wherein said winches provide meansfor detecting a tension of the warping cables.
 13. The system accordingto claim 11, wherein said winches are made with a pulling part,comprising two first drums that wind one of the warping cables for anumber of turns and on a single layer, and an accumulating part,comprising a third drum with a larger diameter than the two first, whichwraps the warping cables, a motorized pulley being provided upstream ofthe two first drums which keeps the one of the warping cables underconstant tension.
 14. The system according to claim 1, wherein saidremote command and control means comprise a software loaded on acomputer, which is interfaced with the tensioning means of the warpingcables, with the means for detecting the quantity of the sedimentremoved by the dredging tool, with the means for detecting the positionof the dredging tool, and with the means for detecting the position ofthe platform.
 15. The system according to claim 1, further comprisingoptical detection means, both surface and submerged, wind detectionmeans, and detection means of a wave state of the water surface whichare all interfaced with the remote command and control means.
 16. Thesystem according to claim 1, wherein the tensioning means of the warpingcables and the means for lifting and lowering means the dredging toolare numerical control machines.